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Help needed diagnosing high fuel pressure readings

Mark33

Well Known Member
Hi gang, I need a little help diagnosing a problem. The fuel pressure readings on my Dynon D-180 started fluctuating all over the place and I?m constantly getting a ?high fuel pressure? alert. The engine is an IO-360 180/HP. equipped with both a mechanical and electric fuel pump along with a red-cube. The engine is running fine and all connections appear to be secure. There?s no rhyme or reason as to when the high pressure alarm goes off. It does it LOP in a low power cruise configuration just as often as it does on takeoff with the electric fuel pump running with high power settings. When I?m looking at the fuel pressure gauge on the EMS page I?m getting constant fluctuations ranging from about 10 psi. all the way to about 40 psi. and it never settles down to any particular steady reading. Like I said above, all connections appear to be good, so where do I start? Fuel filters? Sender? Air trapped in the line? Thanks in advance.
 
Wiring...

Mark,

I would start by checking the wiring at the transducer, then I'd swap the transducer with new/known good one.

Another item to check is fuel pressure reading without the engine running -- just turn everything on and run the boost pump and see what the pressure reading is and how it behaves.

Cheers,

B
 
Also check in the Dynon settings that the fuel pressure sensor is still set to the correct type. If it isn?t, the fuel pressure indication will be all over the place, and not accurate.
 
I?m anxious for an answer to this one too. I have exactly the same indications with my new (to me) O-360 powered RV4, except mine is carbureted and I have the GRT VDO pressure sender/EIS 4000. So help us out please... Thanks. Not trying to rob your thread....
 
You need to find your pressure sensor (red cube is for fuel flow). Then you need to very carefully check the ground connection. Pull the wire at the terminal to make sure it is holding solid and take the connection apart and verify it is clean and to a good ground.

Jay
 
Thanks again gentlemen for the suggestions. Hopefully I?ll have a chance to get back out to the airplane next week and further investigate and verify everything.
 
The fuel pressure readings on my Dynon D-180 started fluctuating all over the place and I’m constantly getting a “high fuel pressure” alert.
I had this problem early in my -9's life. I found the solution to be bleeding the fuel line at the fuel pressure sender. Eventually I put it on my annual condition inspection to do list. It also only happened when I used to have a VDO sender. Now with the Kavlico transducer I don't even have to bleed the system. I think the combination of air in the line with the VDO sender was the problem for me. Hope this helps.
 
Steve,
I took your advice, and the advice of a few others, but your advice to bleed the fuel pressure sender (VDO) worked. I checked the grounds first and they were fine, then I pumped fuel through the line to the sender and re-attached it. Test flight showed completely normal pressures at all power settings and attitudes :).
A couple days earlier, I re-plumbed my fuel lines and fuel filters between the tanks and the fuel selector. They were previously mounted at a steep uphill angle just before the selector. I mounted them a little further from the selector in the RV4 side wells and they are mounted flat, directly inline with the fuel feed line from the tank. My fuel flow was previously all over the place, I assume because of air being introduced because of the suction at the top of those fuel filters. Mounting them flat and a little lower seems to have solved that fuel flow indication problem. 3 flights so far - all is good...

Thanks gentlemen!
 
Update on my high fuel pressure readings

Okay guys, here?s an update to my high fuel pressure warning problem.

1. I checked the brand of fuel pressure sender that I have and it?s a VDO.
2. I checked my wiring for any loose wires, but everything appears good and tight.
3. I bled the line going to the sender, but the problem still persists.
4. When I turn the electric pump on, the pressure?s stabilize and the ?high fuel pressure? warning goes away.

I?m beginning to think that there?s maybe something wrong with the manual fuel pump.

Any more incite on what I should check next will be appreciated.
 
For mark33 responding from the other thread relating to fuel pressure. My problem was with a kavlico fuel pressure transducer. It intermittently told me I had high fuel pressure. On advice from jakej on this forum I unplugged the sensor from the Dynon Skyview and re-plugged it in and problem solved.
 
Update on my high fuel pressure readings

Mark,
The best advice I can give in your case is to replace the VDO unit with the Dynon supplied Kavlico one - they are very reliable
 
I had a similar experience with intermittent high fuel pressure readings using the VDO senders to my Dynon Skyview.
I replaced it with a Kavlico sender and that fixed it. You'll need to add a +5V and Ground wire out to the new sender, and update the Dynon menu that you are using a different type of sender.
 
Hmmm

Mark,

Maybe I've missed this - but what values is the Dynon reporting for Fuel Pressure, and what are the limits (alarms) set to?

Specifically what are the numbers when the engine is running at 1000 RPM, 2000 - 2700 RPM? What are the numbers sitting on the ground with the engine OFF and the boost pump running?

Also, do you have a restrictor installed in the 45? steel AN fitting at the Engine FUEL PUMP connection to the FUEL PRESSURE hose? A picture would be useful.

Thanks!
 
I had a similar experience in my GRT equipped plane a while back. It happened just before OSH so I took the opportunity to quiz Greg - prez of GRT - about it. He said the VDO sensors literally have an arm that wipes across a resistor, and with time the resistor gets a wear spot at the normal reading position. So I replaced mine and all has been well since. He said the piezo electric sensors don?t have that problem - but they cost a lot more :rolleyes:
 
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